1. Field of the Invention
The present invention relates to a lens barrel to which a lens hood can be detachably attached at the front end of the lens barrel.
2. Description of the Related Art
A circular polarizing filter is used over a camera lens to eliminate specular reflection from the surface of objects (e.g. the surface of a glass or the surface of water), or to emphasize the color of the blue sky when using color film. A typical circular polarizing filter (i.e., a screw-setting circular polarizing filter which screws directly onto the front of the lens barrel), which is available on the market, is provided with a mount ring having a male thread portion which is screw-engaged with a female thread portion (accessory mount portion) formed at the front end of a lens barrel, a rotatable filter ring which is rotatably fitted in and supported by the mount ring, and a circular polarizing filter fixedly supported by the rotatable filter ring. When the circular polarizing filter is used, the rotatable filter ring is manually rotated relative to the mount ring with the mount ring being fixed to the front end of the lens barrel.
It is formerly troublesome to use such a circular polarizing filter together with a lens hood. This is because firstly, the rotatable filter ring needs to be rotated to adjust the angle of rotation of the filter without the lens hood being attached to the lens barrel and thereafter the lens hood is attached to the lens barrel to provide a photo-ready condition.
The primary object of the present invention is to provide a lens barrel having a structure which makes it possible to allow the user to rotate the filter even with the lens hood being attached to the lens barrel.
To achieve the object mentioned above, according to an aspect of the present invention, a lens barrel is provided which includes an outer barrel including a lens-hood mount portion at the front end of the outer barrel, a lens hood being detachably attached to the lens-hood mount portion; an inner barrel including a filter mount portion at the front end of the inner barrel and positioned inside the outer barrel to be rotatable about an optical axis relative to the outer barrel; and a manually rotating structure adopted to rotate the inner barrel from the outside of the outer barrel.
With this arrangement, at least two barrels (outer barrel and inner barrel) are provided for attaching the lens-hood and the filter thereto, and the inner barrel which includes the filter mount portion is adopted to rotate from the outside of the outer barrel. Accordingly, a filter which is attached to the front end of the inner barrel can be easily rotated even with a lens hood attached to outer barrel, which facilitates the handling of the lens barrel.
Preferably, the manually rotatable structure includes an operational opening formed on the outer barrel to radially expose part of an outer peripheral surface of the inner barrel through the operational opening.
In an embodiment, the exposed part of the outer peripheral surface of the inner barrel is knurled.
In an embodiment, the manually rotatable structure further includes an operational roller which is rotatably supported by an axial shaft supported by the outer barrel so that an outer peripheral surface of the roller contacts an outer peripheral surface of the inner barrel, the operational roller being operated from the outside of the outer barrel. In this arrangement, it is preferable that the manually rotatable structure includes an operational opening formed on the outer barrel and the operational roller is positioned in the operational opening.
Preferably, at least an outer peripheral surface of the operational roller is made of a friction-enhancing material. For example the friction-enhancing material can be made of rubber.
Furthermore, the axial shaft which rotatably supports the operational roller can be made of a resilient material such as spring steel, so that the operational roller is movable between a transmission position wherein the outer peripheral surface of the operational roller contacts the outer peripheral surface of the inner barrel, and a nontransmission position wherein the outer peripheral surface of the operational roller is separated from the outer peripheral surface of the inner barrel.
In addition to the outer barrel and the inner barrel, a middle barrel positioned between the outer barrel and the inner barrel can be also provided so as to be rotatable about the optical axis relative to the outer barrel. In this arrangement, the manually rotatable structure includes an operational opening formed on the outer barrel to radially expose part of an outer peripheral surface of the middle barrel through the operational opening, and a rotation transmitting device for transmitting rotation of the middle barrel to the inner barrel.
Preferably, the middle barrel is supported between the outer barrel and the inner barrel to be immovable in the direction of the optical axis relative to the outer barrel.
In an embodiment, the rotation transmitting device includes at least one linear guide groove formed on an inner peripheral surface of the middle barrel to extend in the direction of the optical axis; and at least one corresponding projection projecting radially from an outer peripheral surface of the inner barrel to be fitted in the at least one linear guide groove.
Similar to the above-described embodiments, it is preferable to provide a mechanism for easily rotating the middle barrel from the outside of the outer barrel. For instance, the exposed part of the outer peripheral surface of the middle barrel is knurled. Alternatively, an operational roller rotatably supported by the outer barrel can be provided, so that an outer peripheral surface the roller contacts; an outer peripheral surface of the middle barrel.
In the latter instance, the operational roller can be positioned in the operational opening. Furthermore, at least an outer peripheral surface of the operational roller can be made of a friction-enhancing material, such as rubber. The operational roller can be supported by an axial shaft which is made of a resilient material (e.g., spring steel), so that the operational roller is movable between a transmission position wherein the outer peripheral surface of the operational roller contacts the outer peripheral surface of the middle barrel, and a non-transmission position wherein the outer peripheral surface of the operational roller is separated from the outer peripheral surface of the middle barrel.
In an embodiment, a lock mechanism is also provided which locks the inner barrel so as not to rotate about the optical axis relative to the outer barrel. The lock mechanism facilitates attachment of a filter to the filter mount portion of the inner barrel.
Preferably, the lock mechanism includes a female screw hole formed on the outer barrel and a lock screw nut screwed in the female screw hole.
Preferably, the filter mount portion includes a female threaded portion on which a male thread portion formed on a filter mount ring is screwed.
Preferably, either a polarizing filter or a circular polarizing filter is attached to the filter mount portion.
In an embodiment, the lens barrel further includes a stationary barrel which is fixedly attached to a body of an optical instrument, and a movable barrel fitted in the stationary barrel so that the movable barrel is movable along the optical axis relative to the stationary barrel. The outer barrel can be formed integral with either the stationary barrel or the movable barrel.
According to another aspect of the present invention, a lens barrel is provided which includes an outer barrel to which a lens hood is detachably attached at the front end thereof; a rotatable barrel including a filter mount portion at the front end thereof and positioned inside the outer barrel to be rotatable about an optical axis relative to the outer barrel; and an operational opening formed on the outer barrel to radially expose part of an outer peripheral surface of the rotatable barrel through the operational opening, so that rotating force is applied to the rotatable barrel through the opening by the user.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 11-079230 (filed on Mar. 24, 1999) which is expressly incorporated herein by reference in its entirety.